Stereoscopy Guide

What you need to know before making a 3D Movie (Part One)

What steps can you take to ensure your 3D movie is a success? This article tells you what you need to know. Part One deals with depth.

This article will help you:

  • Decide whether your movie needs to be in 3D at all.
  • Decide whether you and your project is worthy of stereoscopy.
  • See the potential pitfalls right at the beginning so you are always in control.
  • Know what to do when, how and at what cost.
  • Decide the right 3D formats for your project.

All of these issues must be addressed, without a shadow of a doubt, before you commit to a 3D project. No exceptions.

This article is written for the absolute novice venturing into stereoscopy (3D, or S3D) for the first time. If you have never attempted 3D before, don’t do it alone, and don’t assume you can deliver a perfect 3D experience.

Panasonic AG-3DA1

If you don’t know your 3D from your 2D, then please read the chapters on stereoscopy in Driving Miss Digital first.

Does your movie need to be in 3D?

There are four major distribution categories for video:

  • Cinema
  • Television
  • Computer
  • Mobile handheld device

The sad truth is, you can’t make one 3D version for all of them. When the screen size or viewing distance changes, the 3D effect changes. It also changes with viewing technology, the display technology and angle of view.

If you are really serious about 3D, and your primary goal is a theatrical release, be prepared to make compromises for the other distribution methods. What does this tell you?

You have to know exactly how and where your movie is going to play before you can even begin. This is the surest test to know if your movie is worth the effort or not. If you don’t know your distribution strategy, exactly, as surely as you know the meaning of these words, then your movie is not ready for 3D.

You may wish it, you may will it, you may force it, but it will come back to bite you in the end. In 3D, you have to know the end, and work your way backwards. If your movie doesn’t stand a chance of a proper 3D release, then it is a waste of time and money to shoot in 3D – unless these things aren’t important to you.

If your project is for television and you don’t have a written contract for a 3D project, you’ll be taking a big gamble. There is no universal demand for 3D TV, and if your material is great, it will find buyers in its 2D avatar.

If your project is for the internet, you need to know exactly what screen types you’re going to cater to – there’s a world of a difference between an iPad, a 13″ laptop, a 15″ laptop and a 21″ computer display. Then you have the thankless task of picking one as your primary device.

If your project is experimental, and you don’t care much about the economics, logistics, workflow and quality of the end result, then please experiment. A few minutes of 3D is great fun. You will learn a great deal. A 3D project that needs to be delivered to a demanding audience is not an experiment.

How do you know good 3D from bad 3D?

Let’s say you know your movie is going to be in 3D, and know exactly which types of screens it’s going to play in. The next thing you need to do is get your eyes checked.

Don’t get me wrong, you’re going to do a lot of technical wizardry down the line to ‘ensure’ your 3D movie is within ‘acceptable norms’. But then, it’ll just be a technical exercise. Is that why you want your movie to be in 3D, or is it because you feel it will really enhance your story in some way?

Like every other aspect of filmmaking, you also need to use 3D as a story-telling device. To do that, you need to know the difference between good 3D and bad. If your eyes are well calibrated and normal you can confidently look at your work. Otherwise, you’ll never be sure what you’re looking at.

What’s the difference between good 3D and bad 3D? For starters, we use our eyes and the way we see 3D space in the real world. Here are some cues:

  • We don’t see the seams between the left and right images, do we?
  • We have a consistent 3D perspective of objects in space, don’t we?
  • Even though the left eye is never the same as the right eye, our brain fuses the images well enough so we don’t perceive the difference, doesn’t it?
  • When a fly sits on our nose, we find the limits of the eye’s ability to converge, don’t we?
  • When we look into the horizon far away, we can no longer perceive depth, can we?
  • Our eyes are at a fixed distance apart, isn’t it?

This is exactly the feeling we need to recreate with our movies. The depth should show, the effort shouldn’t.

How do we manage this? Simple, by avoiding everything that stands in its way! E.g., if you don’t want to see seams between the left and right images, then ensure they aren’t much different. Put your effort where it’s absolutely necessary.

Once you’re comfortable with 3D in general, you can start looking at 3D imagery. You need to test many formats and systems, conduct many experiments, fail, succeed and try again. You will start to see 3D better, even in the real world. You will be alive to depth.

It’s only when you have reached this stage that you can be sure you’re good enough to project your vision to a demanding audience. They can’t see 3D as well as you, so you need to be one responsible. Don’t blame their eyes or the ‘system’.

When the effort behind the 3D shows, it’s always bad 3D. Sometimes you can get away with bad 2D images, but not bad 3D images. It’s like bad audio – everyone hears bad audio. Bad 3D is painful to watch.

How are you going to judge 3D?

Once you know good 3D from bad, you need a partner who will always be dependable. Sure, you’ll have human partners, and we’ll get to that; but you’ll also need a monitoring device that you can rely on.

Remember, this is not just about technical correctness, but also about art. E.g., if your colors are a bit off, you can always hope to correct it in the grading suite. Bad 3D on set doesn’t give you this luxury. If you want an analogy, think of it as overexposing your image with blown, unrecoverable highlights – or recording poor audio on set. Bad 3D is almost impossible to fix.

What are the tools required to judge good 3D? A good 3D monitor. Is it that simple?

Nope. If you’ve read what I’ve written earlier you might have figured it out. If the size and shape of the screen determines the perception of depth, then how can you monitor on set? Surely you don’t expect a filmmaker to carry around a cinema screen and projection system, do you?

No, you don’t. Sad, but true. An on-set monitor will never show you how it’s going to look like on a cinema screen.

It seems like an insurmountable problem but there’s hope. It’s the difference between looking at a 3.5″ LCD and knowing how it’ll play on the big screen. It’s the difference between recording a voice on set and knowing how it’ll sound on the final soundtrack. It’s the difference between watching a snapshot of action and knowing how it’ll be edited together to form one coherent whole. You’re in the twilight zone, and this is where your skill of knowing good 3D, along with the technology that produces it, will see you through.

Your 3D monitoring system becomes your artistic tool – just like a calibrated 2D monitor, professional headphones, or camera blocking and editing. These are all gateways between the reality of your set to the reality of the finished performance. You must be able to stand at the gate, and see both ways.

How deep is your knowledge of depth?

I’m sure you have read Understanding Depth, so I’m not going into what constitutes depth. Knowing it is just the beginning. How do you use depth to tell a story? How do you use it like you use lenses, filters, music, cuts, and so on?

First of all, you must write out what is called a Depth-Script. It’s your shooting script, plus how you’re planning to use depth in each shot.

This exercise will force you to use depth in artistic terms, only when necessary. After all, you don’t need to shove 3D into every scene, just like you won’t plaster a movie with wall to wall music. One hundred plus years of cinema has shown us that 2D is sufficient to cause suspended belief, provided your story is good. Your job is to figure out how you can use 3D to add a visceral experience to that belief, without announcing its existence (like throwing objects at the audience!).

What would you put in a depth-script? You plot exact values or boundaries of the following properties:

  • Inter-axial distance
  • Convergence, or toe-in
  • Stereo window
  • Parallax
  • Duration of each property

I won’t be explaining what these mean because I’ve already done so in Driving Miss Digital. Eventually, you’ll have something that resembles music notation. Without this exercise, you can’t proceed further.

A depth-script with numbers is not very convenient to read, so we have what is called a Depth-Chart:

Depth Chart

The screen plane is your screen. Anything behind it (positive parallax) is under the line (shown in blue). Anything in front of the screen (negative parallax) is above the line (shown in orange).

Each dot represents an object on screen. It could be an actor, a mountain, a helicopter, a water bubble, anything. You can have as many colored lines as you want, whatever is important to you, depth-wise.

We will go into this in detail in the next part.

So, to round up part one of this series, here are the four things you need:

  • Good eyes
  • Good knowledge of stereoscopy – both theoretical and practical
  • A good monitoring system
  • A depth-script or chart

But that’s not all. In Part Two we’ll look at more. We’re just getting warmed up!